Use of existing encoding and modulation techniques such as Optical Frequency Division Multiplexing (OFDM) can be problematic for free-space optical communication, particularly when using optical sources such as light emitting diodes that exhibit a nonlinear intensity as a function of operating current. Similarly, simple pulse position modulation (PPM) can be inefficient from a spectrum consumption perspective, and can cause a perceptible flicker. Such flicker is generally undesirable and can even cause deleterious health effects in certain individuals.